sdk-performance-tools-sysprof-smoke-test: Fix usage of binary capture

Sysprof moved to a binary capture log, so the current machinery parsing the old XML-based format no longer works.

Since this is a smoke test, just check that the capture file exist and is not empty.

This also avoid printing large amount of binary contents to the LAVA log, which makes the log unviewable from the UI and may cause other issues.